Sansui 5050 Diode Bridge replacements

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Hi folks. I have a 5050 that worked fine until one day it didn't. It lights up but won't come out of protection. On the power supply board, two fuse resistors are burnt and measure at 0 ohms, so they're shorted. They are R612 and R613 and I believe they're 10 ohms. I am guessing I need to replace some of the diodes in the diode bridge. Can I replace those with 1N4005s, or should I go higher? If that doesn't take care of it I will go from there, but this has mostly new caps on the PS board already and I am guessing it's a diode issue.
 
On the power supply board, two fuse resistors are burnt and measure at 0 ohms, so they're shorted.
Post a photo please. According to Hoyle ...
R612 is 180Ω 2 watt
R613 is 18KΩ 1/4 watt
 
Let me get this thing on the bench tonight or tomorrow and I'll get back to you with more info.
 
No, they're definitely 10 ohm 1/2W fuse resistors. They measure open line out of circuit. I replaced those and redid the four 3-amp diodes with D5403s and the five 1A diodes with 1N4007s. I think the four big diodes were ok but at least one or two of the 1N4007s measured bad. It works fine now, no issues.
 


I have a question for you. I am working on a 5050 also. I have those two fuse resistors also, but on the back of the board there is another fuse resistor in parallel with each of the two on the components side of the board. I am really confused. The two fuse resistors on the back, each in parallel with one in the front, has what looks to be red-red space silver-silver? Hard to read the silver silver. When I measure the pairs in circuit it is .7 ohms.

Did you find those two resistors on the back of yours? They look to be original. Pretty weird.

I want to replace but I am confused what to replace with. Both sets are 1/2 watt.

One other note. I have the 2701 power supply board. The schematic for that shows a 2.2 ohm resistor.
 
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The two resistors topside are likely bad(open). Somebody was lazy and just soldered a couple replacements to the backside.
 
I have a question for you. I am working on a 5050 also. I have those two fuse resistors also, but on the back of the board there is another fuse resistor in parallel with each of the two on the components side of the board...I have the 2701 power supply board. The schematic for that shows a 2.2 ohm resistor.

On the late production 5050 with the F-2701 board, which was on my bench, there were 10 ohm resistors at R612 and R613 on the topside and underneath there were 2.2 ohm resistors soldered in parallel with each one. So effectively, at R612 and R613, the resistance is 1.8 ohm and has a larger power capacity (0.5 watt to 1 watt).
 
On the late production 5050 with the F-2701 board, which was on my bench, there were 10 ohm resistors at R612 and R613 on the topside and underneath there were 2.2 ohm resistors soldered in parallel with each one. So effectively, at R612 and R613, the resistance is 1.8 ohm and has a larger power capacity (0.5 watt to 1 watt).

Oh, thank you so much for corroborating what I was seeing. I understand Sansui sometimes made changes mid cycle so who knows. Maybe this was one of those.

Thanks again.
 
Correction: went back to my original 5050 notes (instead of just relying on my memory), and the top-side resistors were actually 1 ohm (banding: brown, black, gold, gold) not 10 ohm. Hence, with the parallel 2.2ohm resistors, the effective resistance is ~0.69 ohms. I replaced both resistors pairs with 0.68 ohm/1 watt resistors: https://www.mouser.com/ProductDetail/Panasonic/ERX-1SJR68?qs=gQQ/pDEpiRJP9pSOHHcS%2bw==

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Really appreciate the information. I was having trouble coming up with 10 ohm and 2.2 ohm resistors that fit the bill. .69 ohms makes sense. I was getting around .7-.8 ohms when measuring in circuit. I was a little confused as the OP used 10 ohm resistors as replacements.

Beautiful looking board. So clean. Nice work. Mine looks like a barn find. I don't know where my dad picked this up from.

BTW, did you have to replace the output transistors? I have a pair I have to replace. I have to find some first.

Thanks again.
 
...BTW, did you have to replace the output transistors? I have a pair I have to replace. I have to find some first...

The output transistors in my 5050 were fine; the originals are TO-66 form factor and somewhat difficult to find these days. You can replace with TO-220 types; these ones may be suitable: KSB1017 and KSD1408,
 
The output transistors in my 5050 were fine; the originals are TO-66 form factor and somewhat difficult to find these days. You can replace with TO-220 types; these ones may be suitable: KSB1017 and KSD1408,


One last question. I would like to know what cap you used to replace the 2200uF 63 v power supply cap with. I believe the tall blue one in your photo.

Thanks.
 
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